Abstract The synthesis of a series of novel tricyclic O, N??heterocycles 7a–k, a kind of unprecedented 2??oxo??[1, 2, 4] triazolo [3, 2??d][1, 5] benzoxazepine derivatives, has been accomplished, featuring acid??induced ring closure of the geminal arylazo isocyanato compounds 5, which were prepared from chroman??4??ones in three steps, followed by feasible ring expansion and basic work??up.
![1'-phenylspiro[chromane-4,3'-[1,2,4]triazolidin]-5'-one结构式](https://image.chemsrc.com/caspic/285/720684-25-3.png)
